A tool kit including a handle and a set of bits is often seen. The handle is connected to a selected one of the bits in use. Such a tool kit may additionally include a universal joint or extensive rod for connecting the handle to the selected bit. Such a universal joint renders it possible to use the tool kit in crooked space; it is however not useful in deep and narrow space. Such an extensive rod renders it possible to use the tool kit in deep and narrow space; it is however not useful in crooked space. Therefore, a user has no choice but buying a universal joint and an extensive rod, and this is expensive. Moreover, it is troublesome to switch between the universal joint and the extensive rod.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.